Tantalum is the most common repair metal used in glass-lined equipment because its corrosion resistance is very similar to glass. When this level of corrosion resistance is not required (or inadequate in some instances) other metals are used, such as titanium, gold-platinum or even stainless steel. Some of these materials are less desirable because they are difficult to work with.
Furan, sodium silicate, and potassium silicate cements are often used in conjunction with other repair materials to fill in the spaces under the plugs, patches, or sleeves (these repair methods are discussed later in this article). They typically should not be used on their own, though in some instances sodium silicate cement can be used independently as a temporary repair. These cements all vary slightly in corrosion resistance and should be selected based on the credentials of the chemicals being used in the vessel. The cements consist of a two-part system that requires an accurate powder to liquid ratio, proper mixing, and precise working time to ensure it sets properly. It’s crucial when working with cement to carefully follow the curing times and temperatures to ensure an effective repair.
Epoxy putties are comprised of various epoxy resins that contain nonmetallic or metallic fillers and are used similarly to cement repair materials. Additionally, epoxy putty is used to rebuild metal damage and help provide a level surface for gasket sealing. Epoxy putties are capable of withstanding this compressive stress and have proven to be useful internally for short-term repairs but are otherwise considered inferior to the resistance of furan and silicate type cements.
PTFE gaskets are used to assist and support the metal repair. This material is also used in nozzle sleeves and as a sealing mechanism between the glass lining and the repair material. PTFE can withstand temperatures up to 500°F. In the rare instance that PTFE is not suitable for the process, PVDF or PFA can be substituted.